Antibiotics misuse leads to acquired bacterial resistance, residues in animal products, and environmental pollution. Due to the increased severity of the acquired bacterial resistance, many antibiotics have become ineffective against pathogens. Moreover, antibiotics disrupt intestinal flora and innate immunity in host intestines. Therefore, it has become an urgent need to search for safe and highly effective antimicrobial agents.
Antimicrobial Peptides (AMPs) are important components of innate immunity system against invasion by bacterial pathogens. AMPs have broad-spectrum antimicrobial activities, functioning through mechanisms of membrane disruption, thus are not prone to develop bacterial resistance. AMPs also possess a variety of biological functions, such as stimulation of cell proliferation, activation of the immune system, anti-viral, anti-obesity, and anti-inflammation. As a result, in recent years, a great deal of attention has been attracted to use AMPs as templates for designing new antimicrobial agents. Thus, AMPs have become important breakthrough for the development of new and highly effective alternatives to antibiotics.
α-helical AMPs are the most commonly existing AMPs. The α-helix structure generally contains both hydrophilic residues and hydrophobic residues, and thus possesses amphiphilic properties. Helical AMPs generally do not have significant structural features in the aqueous phase, but exhibit α-helix structure in the lipid-rich cell membrane environment. These types of AMPS exhibit bactericidal effects primarily by disrupting the bacterial cell membrane, leading to gradual degradation of the membrane electrolyte or other signal substances. However, a lot of natural antibacterial peptides are immunogenic, show low antibacterial activity, are unstable, have strong cytotoxicity or high hemolysis, limiting their applications as antimicrobial agents. Therefore, small molecular weight, high antibacterial activity, safety and stability are key factors in achieving the purpose of using antimicrobial peptides to partially replace antibiotics.